Kr-PLIF for scalar imaging in supersonic flows

Experiments were performed to explore the use of two-photon planar laser-induced fluorescence (PLIF) of krypton gas for applications of scalar imaging in supersonic flows. Experiments were performed in an underexpanded jet of krypton, which exhibited a wide range of conditions, from subsonic to hypersonic. Excellent signal-to-noise ratios were obtained, showing the technique is suitable for single-shot imaging. The data were used to infer the distribution of gas density and temperature by correcting the fluorescence signal for quenching effects and using isentropic relations. The centerline variation of the density and temperature from the experiments agree very well with those predicted with an empirical correlation and a CFD simulation (FLUENT). Overall, the high signal levels and quantifiable measurements indicate that Kr-PLIF could be an effective scalar marker for use in supersonic and hypersonic flow applications.     

From extended solids to nano-scale actinide clusters

Selected highlights of more than a decade of research efforts concerning the structural chemistry of actinyl materials at the University of Notre Dame is reviewed, with an emphasis on complex topological arrangements of polyhedra to form extended structures and frameworks. Earlier work focused on structures of uranyl minerals and synthetic compounds, with increasing emphasis on neptunyl materials and the importance of cation–cation interactions in their structural details and properties. Much of the research over the past 5 years has examined a growing family of nano-scale clusters of uranyl peroxide polyhedra containing from 16 to 60 polyhedra. These clusters contain topological squares, pentagons and hexagons, and six have adopted fullerene topologies with 12 pentagons and an even number of hexagons.     

Predictive modeling of positive mode IMS gas-phase ionization: is 2nd-order Møller-Plesset perturbation theory adequate?

Low level ab initio Quantum Chemistry (QC) is shown to be a promising technique for predicting the relative ordering of a wide variety of potential analyte, dopant, and interferent molecules, by their proton affinities (PA). Computed PAs, using a single level of chemical theory, are summarized for 53 compounds and when compared to literature reference data have a mean unsigned error of ∼9.5 kJ/mol. Where applicable, multiple conformations of the protonated species were explored. In these cases, the Boltzmann weighted PA is reported. Finally, examples are shown in which QC modeling is used to predict potential fragmentation products initiated by the positive mode ionization.     

Postponement in New Product Introduction

Agility has now been a main research topic in the l it erature. There is much written on agility mainly focusing on manufacturing p rocess and strategic processes. However, we argue that new product introduction should call for agility as well due to uncertainty about technological advances and customers‘ demand. A technological superiority alone may not guarantee succe ss for new product introduction. We focus on the role of postponement for two ma in processes in new product introduction: new product ...     

Three-dimensional numerical modeling of geoacoustic scattering from seafloor topography

A three-dimensional (3-D), second-order finite-difference method was used to create synthetic seismograms for wave propagation in heterogeneous media in order to investigate the scattering of elastic and acoustic energy due to topography on the seafloor. The method uses a fully staggered grid in Cartesian coordinates as developed by Virieux [Geophysics 51, 889-901 (1986)]. Numerical results were generated for two models: a linear fault scarp on the seafloor, and a flat seafloor containing a rectangular channel. Wave-front snapshots allow the scattering and focusing of different wave modes with direction to be visualized. Compressional and shear wave backscattering from the sides of the features can be seen together with the trapped compressional wave energy propagating inside the channel. The results illustrate the effects of out of the plane scattering due to simple seafloor topographic features.